Water resistant coatings for photographic paper and method for producing same



United States Patent O inenting. (ci. 95.58,).

This invention relates to` alproess for treating paper with a reSinlateX coating which may er may netherlamented and which may bewaterproofeor waterresista'nt'.

Waterproof coatings of paper, fabrics and other absorbent materialsarewell known. Various waxes have beennced tciinnart Water recietance.by. lleating tlle. waX treated. material Se that tile.-

Pertneatee tite SticeS cf the material In` addition. VariQnS Syn...teSinS have been need. commercially especially te treat fabricSin theclothinaand. weaving indnetriea P11. cgraphieparlerL has cftelnbeennnade. Water reeietantny coating with ancellulose lacquer, but thisprocess isnn- Snitfalale in. certain instances ,fer generalpaper mill..nte dne te thevclatilennlvents nSedand resnltantltaaarde The abovemethods have been found generally unsatisfactory in making .aWaterfresis'tant paper which may be. need. pheteataphieally, andvwhich.. lSf compatible with photographic emnleienet dyes andproceseinglcllentlcala Iier. instance) the nee et a treatment. nlaycancea gelatin eninlSien te peel freni. the. paper. Other. treatments snch asresin coatings from `solvent solutions or ligtnielt Permit abScrntiencfdyes inte.tllteiJaPer1 caating resulting instaining andotherobjectionable'after eiect'sw. It has also. been fcnndthat Seinecf the.Water-teSiStant enti-.aces perniitretentien cf processingchenicalein-'tlle Paper which later aiect. the. photographic itnageS.-

Accordingly, it is desirable to have a photographic paper base whichiseither completelyl or partially resistant to Water and particularly.tolthe processing soluticne in which tlie Paper immersed. Snclitarer.ccnld be rapidly processed Without` retention of the. chemicals in thebase and cenld be Saneegeed dry yter. immediate nee- For inetance,Partially reSiStant Steck might been# i'iciently temporarily resistantto Awater orphotographic processing solutionsy to permit contact with ashee'tl'wet vvith water or chemicals for a few seconds Without suf,-licient wetting ef. the. Stcele tocante. cocltle andtnettlecr similardefects and yet have a Waterresistange balanced in such a manner as tobe receptive tothe transfer of a gelatin image.

An object of this invention is to provide a waterresistant paper- WhichWillpermit/thel application of g a,- tin solutions or other similarWater based materials Withf out repellency, and to Ywhich the gelatincoating adhere during immersion in Water or photographic 'processingsolutions. Another object of this invention is to providel awater-resistantcoating which will. have low or ne ligible absorption forchemical dyes, which willhave substantially the saine thermal expansionproperties as gelatin, and which will form a continuous lm freeofholes,v A further object is to produce a water-resistant paper WlteSeSlieetS will remain Separate and individual ander pressure in roll formor in cut sheets. Another objectI is to provide paper which resiststheabsorption. of water or chemical solutions in such quantity astocause stain or change in physical characteristics during contat-vpeniodsup to sixty seconds. Another.l object is to provide a water-resistant*paper` receptive` to. the. transfer of a gelatin image, but suflicientlyWateLreSistantLas-to eliminate exceaewettine t 2: The altere eltiecteatecbtainedgtlncngh cataratta et coating a. .Snltalile bate nlaterlalwitli.a ntintn're cita/s1 resins which forms a good, clear, Water-white`water.- proof iilm. This mixture contains.,essentially'61) a'soft resinlatex formed by the polymerization of styrene with butadiene, and (2) aAhardl polystyrene latex. This mixedsystem is unique in` that it hasbetterlrn forming properties; than, a system. containing the.sameoverall ratio of styrene, to butadiene that isvobtainedf d nringanorni a l fpo1yn 1eri zation. In the. preferred: embodiment of ourinvention, the mixture ofthe. polystyrene.. resin latex and thestyrene-butadiene vresin latex was applied by a suitable method to theface of baryta coated stock. The resin latexcoating, afterdryingwaspassedlin front of a Abank of-'infraredheatersat such arateastobring the.coated,paper. to a temperature between180to 320 Tlhis.-.re.s,ults ixi`,a.Water-resistant paper. coatingcompatibl withgelatincoatings suitableforuses as descrbedfaboxze. The following.examplesv are... given. by.. vvay,y of.: illustra.- tion and it isunderstoodthatthe. invention is not limited there@ EXAMPLE. I.

A fell. eil? 1b... per. 1QQ0..Saftniietegfapllic. laaae ice SteeleWaeceated with twc. .2.0 snif/Sa. inetercaa'ts. .baryta (1.19.6 byweight) en ille face aide. ant/SS1- tneter' ccat' vef' pelyetyrene feSinlaten-f.. y tntadiene. laten. .cern inaticn (4515.5 tay'y .c lilleWeight). was.. applied .by a.. .Suitable inetllnd te ttt-.e flaca et thebaryta coated stock. The resin latex coating, after drying, was passedinfront offa bank of infrared heaters at sucha rate as to bring thecoated paper to `a temperatureofv 3009' F; at-the lastlheater. A "125gm-JsQirieter coat composed of-equal parts. (by solids Weight) "oufl"the above resinlatexmixturefand gelatin then applied-on the face side.This'gel-resin subcoat serves two purposes: (l1.) To prevent blockingbetween the face side'and vire side coats, and (2) toy act as a subcoatA(bin-rider?) between the resin latex coating and the 'gelatineniulsioinThe subcoat-Was also heat treated in the fab-ove described manner. 2Qgm./ sq. meter coat offthe saine reslnla'tex combination was lthenapplied` to the vvire side and nheat treated. The paper so coated wassensitized `vv-itiwa"..Suitable photographic emnlsilon.' After normalphotographic processing and washing, the excess Water was removed with atpengeer towel and thepnnt.waS-.sumcientlymy ter reaecnablynennal.landline` Fnrthenten cited that thepaper was-canal tc crfbetten tlianlteilaneelrent Waterproofness of resin latex coated papeliys. dope coated(celluloseacetate.butyrqtejn siv'enr) paper Latex l Dope .QeateliCoated.

Moisture Retention l. Y I Hypo Retention 2 1n- 1g Processing sizechange:

L -.0.4 .2o 10' 39 .0.2" .o 01 .04r l Valley PenetrationT l After mininprocessing solutions, surface'w'l ed-Wi lry 2 After 1 min; indeveloper', 10 min; in hypo, 2 mig. wasli. S/Iollllgi'grams per Squawmeh' a.. l; .mwa-o.. 'ZottyllceHnchange sine per lzchange Ln relativehumidity. t(30%- 4 l min. developer, 2 min. hypo, 3 min. Water,consecutive exposures. Morsltnro gain, gramsper sq. om. (test forWaterrpernieahilitmfleclinaal-association of the Pulp'andlaper Industrymethod T 4f1lm).

The Valley penetrationt'e'st is described inT. AIP. P.' T."Inst'r`mentatien Study XVI, Q nrrclaticnBetweenine.Deereeotsizinaasfnetemined byValley; T-. AJP. PIf'and Currier Methods!" 3 EXAMPLE n Photographic basestocks varying in weight from 2() lb. to 40 1b./ 1000 sq. ft. werebaryta coated, resin latex coated, subbed, and sensitized in the mannerdescribed in Example I. Testing of the processed photographic stockshowed waterproofness comparable to that described in Example I.

EXAMPLE III A suitable photographic base stock was coated with one 20gm./sq. meter coat of baryta instead of two 20 gm./sq. meter coats ofbaryta. After resin latex coating, subbing and sensitizing in the mannerdescribed in Example I, the stock so prepared showed waterproofnesscomparable to that of Example I.

EXAMPLE IV A suitable photographic base stock was coated with 20 gm. ofbaryta having a gelzixe ratio of 1:16 instead of the 1:9.6 ratiodescribed in Example I. After resin latex coating, subbing, andsensitizing in the manner described in Example I, the stock so preparedshowed waterproofness comparable to that of Example I.

EXAMPLE V A suitable photographic base stock was resin latex coated andsubbed in the manner described in Example I. A 20 gm. coat of baryta(gekxe ratio varying from 1:9.6 to 1:16) was applied over the subbing,and the stock so prepared was sensitized with a suitable photographicemulsion. The stock had waterproofness comparable to that of the stockprepared in Example I.

EXAMPLE VI A suitable photographic base stock was resin latex coated onthe face side only and subbed in the manner described in Example I. A 20gm. coating of baryta (gelzxe ratio of 1:16) was applied to the faceside and the stock so prepared was sensitized with a suitablephotographic emulsion. The stock so prepared was suitable for very rapidprocessing where the hot processing chemicals are sprayed on the faceside of the stock and the wire side receives no wetting. The stock wasalso suitable for the chemical or photomechanical transfer ofphotographic images to the face side without mottle, cockle, etc.

EXAMPLE VII A suitable photographic base stock was coated with 2Ogm./sq. meter of baryta (1:9.6, gelziixe ratio) and then was resin latexcoated on the face side only and subbed inthe manner described inExample I. The sensitized stock was suitable for the uses described inExample VI.

EXAMPLE VIII A roll of suitable photographic base stock was barytacoated as in Example I except that an additional 20 gm. coat 4of barytawas coated on the wire side. The stock was then resin latex coated,subbed, and sensitized as in Example I with comparable waterproofness.

EXAMPLE IX Samples of suitable photographic base stock were barytacoated with two 20 gm. coats of baryta (1:9.6 gelzxe ratio). The paperwas then coated with resin latex combinations in which the polystyreneresin latex to styrene-butadiene latex ratio was varied from 50:50 to100 (by solids weight). The coatings were heat treated, subbed, andsensitized in the manner described in Example I. While thewaterproofness was comparable on all samples, it was found that theoptimum range with regards to non-blocking, color, heat and lightstability, and general handling properties -was from 50-50 to 40-60(styrenestyrene-butadiene by solids weight). Below the 40-60 ratio thecoatings had a tendency to be yellow and tacky.

EXAMPLE X Baryta coated photographic paper, prepared as in Example I,was coated with a 20 gm./sq. meter coat of polystyrene resinlatex-styrene-butadiene resin latex combination (45:55 by solidsweight). Samples were heat treated at temperatures ranging from 180 F.to 350 F. (temperature of coated paper at last heater). The samples werethen subbed; heat treated at the same temperatures as for the facecoating; coated on the wire side and heat treated at the sametemperature; and sensitized with a suitable photographic emulsion. Allsamples showed waterproofness comparable to that of Example I. However,it was found that a temperature range of 240*300 F. was optimum toprovide good gloss, antiblocking qualities, and adequate adhesionbetween the subcoat and latex coat.

EXAMPLE XI Suitable photographic base stock was baryta coated as inExample I. Using a polystyrene resin latex-styrenebutadiene resin latex(45:55) combination, coating weights varying from 10 gm./sq. meter to 30gm./sq. meter were applied to the face side. Similar weights of the samelatex were applied to the wire side after subbing. It was found that the10 gm. coatings oifered temporary water resistance for some purposes butthat 15-20 gms. was optimum for good waterproofness.

EXAMPLE PGI Photographic base stock was baryta coated and resin latexcoated on the face side as in Example I. Snbcoatings (1.5 gm./ sq.meter) were applied in which the resin latex to gel ratio was variedfrom -40 to 30-70 (by solids weight). The wire side coating was thenapplied and heat treated as in Example I. After sensitizing with theproper photographic emulsion, it was found that the entire range ofresin-gel ratios provided adequate emulsion adhesion for some purposes.However, it was found that the optimum range for Vbest adhesion was from50-50 to 30-70 resin to gel.

EXAMPLE XIII Photographic base stock was baryta coated as in Example I.A resin latex coating composed of from to parts of the poly-styreneresin latex and styrenebutadiene latex combination, and from 30 to 20parts of gelatin by weight was applied at a laydown of 20 grn./ sq.meter. The coating was heat treated as described in Example I and thewire side coating was applied and heat treated. The resulting stock wassensitized with a proper photographic emulsion and was found to havewaterproofness comparable to that of Example I. In addition, `\t wasfound that the addition of gelatin to the resin latex .combinationprovided adequate adhesion (for some pur- A roll of suitablephotographic base stock was baryta coated, resin latex coated on theface side, and subbed with proper heat treatment between coatings. Thentwo consecutive 10 gin/sq. meter coatings of the same resin vlatex wereapplied to the wire side instead of one 20 igm./ sq. meter. Each coatingwas heat treated separately. After sensitizing with the properphotographic emulsion, it was found that the dual l0 gm. coatingsprevented the penetration of the processing chemicals through weak spotsin the coating when the stock was under the cinching pressure of thestandard roll processing equipment or when there was considerablehydro-static pressure as in deep tank processing.

The above examples show our use of the water-resistant coating to paperto be used for photographic purposes. However, the coating mixture shownabove could also be applied to any suitable absorbent base material suchas cloth, leather and the like. In addition, various coating methods maybe used in applying this resin composition to the paper. As can be seenfrom the above examples, there may be variations in the paper stockweight, number and weight of baryta coatings, gelriixe ratio in thebaryta, position of the resin and baryta coatings, ratio of polystyreneto styrene-butadiene, temperature of heat treatment, resin coatingweight, subbing formula and amount of gelatin, if any, added to thecoating mixture.

The polystyrene resin which we use for 100% polystyrene contains from 32to 50% resin solids. The styrene butadiene latex contains from 60 to 67%styrene and from 40 to 33% butadiene and has 43-55% solids.

Various coating means may be used which are within the scope of ourinvention. For example, a reverse roll coater, air knife doctor, coatinghopper or the like may be used. Heating methods include infraredheaters, infrared blankets, and any other suitable method to obtain thedesired temperature. Heat treating temperature is referred to above asthe temperature of the coated paper as it passes in front of the lastheating unit. Generally, the paper is passed in front of the heaters atsuch a rate as to obtain the temperature in about tifteen seconds, butthis time is not considered critical and other time periods may be usedto accomplish the purposes of this invention.

In photographic uses it is advantageous to apply a subbing coat over thewaterproof coating as shown above in Example I. This subbing coat isapplied from a water system and acts as a binder between the resincoating and photographic emulsion coating. However, it is alsoadvantageous to add gelatin to the resin coating mixture. The resultingcoating permits the application of a photographic emulsion directly onthe water resistant surface without additional subbing.

This process for forming a water-resistant and waterproof coating forpaper meets a need in the photographic industry for a waterproof surfacewhich is compatible with a gelatin emulsion, and which resists stainingby photographic dyes and chemicals.

In view of the many changes and modifications which may be made Withoutdeparting from the principles underlying the invention, reference shouldbe made to the appended claims for an understanding of the scope of theprotection afforded this invention.

We claim:

1. A process for preparing a photographic brous sheet base materialcomprising the successive steps of coating the material with a coatingcontaining baryta, drying, coating with a mixture containing from 40 to60% polystyrene resin latex and from 60 to 40% styrene-butadiene resinlatex, drying, and heating to a temperature between 180 to 320 F.,applying a subcoating containing from about 30 to 70% gelatin and from70 to 30% of a mixture containing from 40 to 60% polystyrene resin latexand from to 40% styrene-butadiene resin latex, drying, and heating to atemperature between about 180 to 320 F., and coating with a photographicgelatin emulsion containing light-sensitive silver salts over thesubcoating.

2. A process according to claim 1 wherein the base material is paper.

3. A process for making a photographic fibrous sheet base materialcomprising the successive steps of coating the material with a mixturecontaining from 40 to 60% polystyrene resin latex and from 60 to 40%styrenebutadiene resin latex, drying, and heating to a temperature ofabout 180 to 320 F., applying a subcoating containing gelatin and amixture of from 40 to 60% polystyrene resin latex and from 60 to 40%styrene-butadiene resin latex, drying, and heating to a temperaturebetween 180 to 320 F. and coating with a photographic gelatin emulsioncontaining light-sensitive silver salt.

4. A process according to claim 3 wherein the base material is paper.

5. A process for making a photographic paper comprising the successivestepsv of coating the paper with a mixture containing from 30 to 70%gelatin and from to 30% of a mixture containing from 40 to 60%polystyrene resin latex and from 60 to 40% styrene-butadiene resinlatex, drying, and heating to a temperature between about to 320 F., andcoating with a photographic gelatin emulsion containing light-sensitivesilver salts.

6. A water resistant photographic paper produced in accordance with theprocess described in claim 1.

7. A water resistant photographic paper produced in accordance with theproces described in claim 2.

8. A water resistant photographic paper produced in accordance with theprocess described in claim 3.

9. A water resistant photographic paper produced in accordance with theprocess described in claim 4.

10. A water resistant photographic paper produced in accordance with theproces described in claim 5.

References Cited in the le of this patent UNITED STATES PATENTS2,284,877 Martinez June 2, 1942 2,491,023 Alles et al. Dec. 13, 19492,574,439 Seymour Nov. 6, 1951 2,614,089 Harrison et al. Oct. 14, 19522,614,093 Wheelock Oct. 14, 1952 2,650,163 Horsey et al. Aug. 25, 1953FOREIGN PATENTS 644,022 Great Britain Oct. 4, 1950

1. A PROCESS FOR PREPARING A PHOTOGRAPHIC FIBROUS SHEET BASE MATERIALCOMPRISING THE SUCCESSIVE STEPS OF COATING THE MATERIAL WITH A COATINGCONTAINING BARYTA, DRYING, COATING WITH A MIXTURE CONTAINING FROM 40 TO60% POLYSTYRENE RESIN LATEX AND FROM 60 TO 40% STYRENE-BUTADIENE RESINLATEX, DRYING, AND HEATING TO A TEMPERATURE BETWEEN 180 TO 320*F.,APPLYING A SUBCOATING CONTAINING FROM ABOUT 30 TO 70% GELATIN AND FROM70 TO 30% OF A MIXTURE CONTAINING FROM 40 TO 60% POLYSTYRENE RESIN LATEXAND FROM 60 TO 40% STYRENE-BUTADIENE RESIN LATEX, DRYING, AND HEATING TOA TEMPERATURE BETWEEN ABOUT 180 TO 320*F., AND COATING WITH APHOTOGRAPHIC GELATIN EMULSION CONTAINING LIGHT-SENSITIVE SILVER SALTSOVER THE SUBCOATING.
 6. A WATER RESISTANT PHOTOGRAPHIC PAPER PRODUCED INACCORDANCE WITH THE PROCESS DESCRIBED IN CLAIM 1.